Although this does provide accurate guidance on how to use these utilities some limitations must be understood. Let’s address the easy stuff first…..

If you use an externally controlled overwrite process to clear data from hard drive devices in the SCSI family, the overwrite process will have the ability to access all data storage regions of the media surface, as the software will have be capable of instructing the controller to access all data blocks.

According to the UCSD Center for Magnetic Recording Research a single pass process is often sufficient to provide adequate protection from reconstruction. Edge track phenomenon was at one point a concern. However, in high capacity storage hardware where the concern for the capacity per Sq. cm. is a priority for manufacturers, there is in fact no track edge where recoverable information can exist. As I recollect the gap between tracks on current production hardware is no greater than 10 Microns, and contains nothing more than magnetic noise.

In the case of ATA family drives, the interface controller and the drive control electronics are embedded on each drive and share a privileged relationship. Meaning that there are limitations to the external controls that can be issued to the drive. This limitation includes the ability to externally issue commands to access or address any bad blocks, or protected regions, such as the Host Protected Region (HPA), or storage areas beyond the Device Control Overlay (DCO) range.

Accordingly, due these limitations, overwrite software from any vendor CAN NOT address all data storage areas of ATA spec devices. A more reliable process that can purge all regions of an ATA device would be to use the technology already embedded in the drive electronics called Secure Erase.

Developed by the UCSD as a standards based purge technology. Secure Erase has been a component of the ATA spec since 2001, and is present in all ATA Spec compliant hard drives since this date (and in some as far back as 1999). Despite many software vendors deliberately attempting to obfuscate the presence of this technology by using the term ‘Secure Erase’ as a description of their overwrite product, Secure Erase is a more reliable process on ATA spec devices than any software based overwrite product.

There are a number of resources available on Secure Erase. I would start with the National Institute for Standards and Technology to get an idea of what is considered as acceptable decommissioning practice. The NIST has published Special Report 800-88 that covers the acceptable means to decommission all types of data storage.

Alternately, I would be glad to offer further information or guidance on the topic.

I can be reached at ryk@converge-net.com